Wavelength-Selective Shape Memory Alloy for Wireless Microactuation of a Bistable Curved Beam

Wireless and/or sensorless components offer a great potential for friendly integration in mechatronic systems. This paper presents a wireless technique to actuate a bistable curved beam using wavelength-selective shape-memory-alloy (SMA) thin foils. The SMA thin foil is irradiated remotely by continuous-mode laser diodes of 785 and 658 nm wavelengths. First, a comparison between two numerical thermal models is done. These models obey the same conduction and convection equations but the effect of phase transformation is integrated in two different ways. A good agreement is found between the two simulation results. Then, the force generated by the SMA sample (size: 3 mm x 1 mm x 0.1 mm), during martensite-to-austenite phase transformation, is experimentally measured using a miniature force sensor. The force comes out to be 403 mN with 70 mW laser power. Using this force value, a bistable curved beam is designed and fabricated by rapid prototyping technique. Optical filtering layers, which are responsible for the wavelength-selective response, are directly deposited onto the SMA samples. Finally, two SMA samples are used to switch the curved beam between its two stable positions.